Collard and kale-Diamondback moth

Plutella xylostella

Pest description and crop damage Diamondback larvae are smaller than most other caterpillars in cole crops, about 0.31 inch when full grown. The larval body is wider in the middle and tapers at both ends, with two legs (prolegs) on the last segment forming a distinctive V-shape at the rear end. When disturbed, the larvae wiggle frantically or rapidly attach a silken line to a leaf and drop over the edge. Larvae feed mostly on outer or older leaves of older plants, chewing out small holes, or at the growing points of young plants. They also feed on floral stalks and flower buds.

Adult moths are small, slender, and grayish brown. Male moths display three diamond-shaped markings on their back. In the Pacific Northwest, the damage from diamondback moth is not so much from feeding as from contamination by pupae. Late stage instars crawl into stems infesting harvested crops.

Biology and life history Cabbage is the preferred host, but it also attacks all cole family crops. The adult overwinters in trash in and around fields. Adults emerge in May and early June and lay eggs singly or in twos or threes mainly on the upper sides of leaves. The eggs are minute. They hatch in 4 to 8 days. Larvae feed mostly on the undersides of outer or older leaves of older plants, chewing out small holes, and mature in 10 to 30 days. They then spin loose white cocoons, which they attach to leaves or stems, and pupate within them. Adults emerge in 10 to 14 days. There may be two to four overlapping generations each year.

Pest monitoring Natural enemies and insecticides applied to control other pests keep the diamondback moth under satisfactory control in most fields, but keep records of diamondback moths as you monitor for other caterpillars. Adult moths frequently migrate from fields being harvested or disked under.

In Minnesota, the action thresholds for diamondback moth in cabbage are: Where diamondback moth is the primary insect pest (usually early-year), before cupping, treat with Bacillus thuringiensis if 50% of plants are infested with five or more larvae each. After cupping, treat if 10% of plants are infested with one or more larvae each.

Management-biological control

Natural enemies, including an ichneumid wasp and the egg parasite Trichogramma pretiosum, often effectively control diamondback moth in California. Therefore, consider the level of parasitism when making control decisions. Clearly, Bt is much easier on the beneficial insects, and its use, when needed, helps conserve the beneficial insect complex.

Management-chemical control: HOME USE

• acetamiprid
• azadirachtin (neem oil)-Some formulations are OMRI-listed for organic use.
• Bacillus thuringiensis var. kurstaki (Btk)-Some formulations are OMRI-listed for organic use.
• carbaryl
• cyfluthrin
• esfenvalerate-Do not use on kale.
• insecticidal soap-Some formulations are OMRI-listed for organic use.
• malathion
• permethrin
• pyrethrins-Some formulations are OMRI-listed for organic use.
• spinosad-Some formulations are OMRI-listed for organic use.
• zeta-cypermethrin

Management-chemical control: COMMERCIAL USE

• alpha-cypermethrin (Fastac EC) at 0.014 to 0.025 lb ai/A. PHI 1 day. REI 12 hr. Retreatment interval 7 days. Do not exceed 0.075 lb ai/A per season.
• azadirachtin (Neemix 4.5-B) at 0.014 to 0.035 lb ai/A. PHI 0 days. REI 4 hr. OMRI-listed for organic use. Not registered for use in OR.
• Bacillus thuringiensis (Javelin)-See product labels for rates. PHI 0 days. REI 4 hr. Slow acting. May need multiple applications. Add an appropriate spreader-sticker to enhance control. Most effective on small larvae. Some formulations are OMRI-listed for organic use.
• beta-cyfluthrin (Baythroid XL) at 0.019 to 0.025 lb ai/A. PHI 0 days. REI 12 hr. Retreatment interval 7 days. Do not exceed 0.1 lb ai/A per season.
• bifenthrin (Brigade 2EC, Sniper) at 0.033 to 0.1 lb ai/A. PHI 7 days REI 12 hr. Retreatment interval 7 days. Do not exceed 0.4 lb ai/A per season.
• bifenthrin/imidacloprid (Brigadier) at 0.06 to 0.095 lb ai/A. PHI 7 days. REI 12 hr. Do not exceed 0.24 lb ai/A imidacloprid and 0.24 lb ai/A bifenthrin. Retreatment interval 7 days. Maximum 5 treatments only after bloom.
• bifenthrin/zeta-cypermethrin (Hero EW) at 0.04 to 0.1 lb ai/A. PHI 7 days. REI 12 hr. Retreatment interval 7 days. Do not exceed 0.45 lb ai/A per season.
• borate complex (Prev-Am Ultra) applied as a 0.4% solution. Spray to complete coverage. REI 24 hr. Retreatment interval 7 days. OMRI-listed for organic use.
• Burkholderia spp. (Venerate XC) at 1 to 4 quarts/A product. PHI 0 days. REI 4 hr. OMRI-listed for organic use.
• carbaryl (Sevin XLR Plus) at 1 to 2 lb ai/A. PHI 14 days. REI 12 hr. Limit 4 treatments per year. Do not exceed 6 lb ai/A per crop. Retreatment interval 7 days.
• chlorantraniliprole (Coragen) at 0.045 to 0.065 lb ai/A as soil, chemigation or foliar treatment. PHI 3 days. REI 4 hr. Limit 4 treatments per crop. Retreatment interval 3 days foliar, 10 days drip chemigation. Do not exceed 0.2 lb ai/A per season.
• chlorantraniliprole/thiamethoxam (Voliam Flexi) at 0.1 to 0.175 lb ai/A. PHI 7 days. REI 12 hr. Retreatment interval 7 days. Do not exceed 0.172 lb ai of thiamethoxam or 0.2 lb ai of chlorantraniliprole per acre per growing season.
• Chromobacterium subtsugae (Grandevo) at 0.3 to 0.9 lb ai/A per 100 gal. PHI 0 days. REI 4 hr. OMRI-listed for organic use.
• cryolite (Kryocide) at 7.7 to 15.4 lb ai/A. PHI 14 days. REI 12 days. Do not exceed 92 lb ai/A per season. Collards only. OMRI-listed for organic use. Product not registered for use in OR.
• cyantraniliprole (Exirel) at 0.045 to 0.88 lb ai/A. PHI 1 day. REI 12 hr. Retreatment interval 5 days. Limit 6 treatments per year. Do not exceed 0.4 lb ai/A per year.
• cyclaniliprole (Harvanta 50SL) at 0.036 to 0.054 lb ai/A. REI 4 hr. PHI 1 day. Limit 3 treatments per crop. Retreatment interval 5 days. Do not exceed 0.22 lb ai/A per year. Product not registered for use in WA.
• cyfluthrin (Tombstone) at 0.038 to 0.05 lb ai/A. PHI 0 days. REI 12 hr. Retreatment interval 7 days. Do not exceed 0.2 lb ai/A per season.
• emamectin benzoate (Proclaim) at 0.0075 to 0.015 lb ai/A. PHI 14 days. REI 12 hr. Do not exceed 0.06 lb ai/A per season. Retreatment interval 7 days. Do not graze.
• GS-omega/kappa-Hxtx-Hv1a (Spear Lep) at 0.02 to 0.04 lb ai/A (1 to 2 pints/A). PHI 0 days. REI 4 hr. Do not exceed 1.7 lb ai/A per year.
• indoxacarb (Avaunt) at 0.045 to 0.065 lb ai/A. PHI 3 days. REI 12 hr. Do not exceed 0.26 lb ai/A per crop. Limit 5 treatments per year. Retreatment interval 3 days.
• malathion (Malathion 8) at 1.0 lb ai/A. PHI 7 days. REI 12 hr. Retreatment interval kale 5 days, collards 7 days. Limit 3 applications.
• methomyl (Lannate SP) at 0.45 lb ai/A. PHI 10 days. REI 48 hr. Do not exceed 5.4 lb ai/A collars per year. Fresh market Collards only.
• naled (Dibrom 8E) at 0.94 lb ai/A. PHI 1 day. REI 48 hr. Retreatment interval 7 days. Do not exceed 9.4 lb ai/A per year.
• spinetoram (Radiant SC) at 0.039 to 0.078 lb ai/A. PHI 1 day. REI 4 hr. Retreatment interval 4 days. Do not exceed six applications or 0.266 lb ai/A per year. Do not apply to seedling cole crops grown for transplant within a greenhouse, shade house, or field plot.
• spinosad (Success, Entrust SC) at 0.023 to 0.062 lb ai/A. PHI 1 day. REI 4 hr. Do not exceed six applications or 0.45 lb ai/A per crop. Entrust SC is OMRI-listed for organic use.
• thiamethoxam/chlorantraniliprole (Durivo) at 0.195 to 0.257 lb ai/A applied to the soil. PHI 30 days. REI 12 hr. Do not exceed 0.172 lb ai of thiamethoxam or 0.2 lb ai of chlorantraniliprole per acre per growing season.
• tolfenpyrad (Torac) at 0.17 to 0.21 lb ai/A. PHI 1 day. REI 12 hr. Retreatment interval 14 days. Limit 4 treatments per year. Do not exceed 0.42 lb ai/A per year.
• zeta-cypermethrin (Mustang) at 0.028 to 0.05 lb ai/A. PHI 1 day. REI 12 hr. Retreatment interval 7 days. Do not exceed 0.3 lb ai/A per season.